The response of the intact left ventricle to overload states is incompletely understood. The duration and severity of the overload stimuli which produce hypertrophy alone and hypertrophy with subsequent left ventricular failure have not been elucidated. This study is designed to evaluate the response of the left ventricle to graded degrees of pressure overload produced by aortic banding in dogs and to volume overload produced by long term chronic exercise in dogs. Ventricular mechanical function will be evaluated in the intact anesthetized dog using cineangiography with computer based quantitative image analysis of left ventriculograms. With this method a multiparametric evaluation of mechanical function is possible. Myocardial contractile protein changes will be evaluated in hypertrophy by measuring cardiac myosin ATPase activity. Similar studies will be undertaken after production of hypertrophy and following removal of the hypertrophic stimulus. A method for analysis of left ventricular performance in the awake, intact dog will be developed using radiopaque markers surgically implanted in the left ventricular myocardium. This method will be applied to the analysis of ventricular function in the intact dog with left ventricular hypertrophy. These studies will improve understanding of the mechanical alterations of the heart in hypertrophy, the differences between volume and pressure overload hypertrophy, the reversibility of myocardial lesions in hypertrophy, and the cardiac response to exercise.